The invention relates to a system for automatically selecting one or more scalers available in a video system.
Continual advances in computer technology are making possible cost-effective, yet high performance computers capable of displaying high resolution images. A variety of display devices, including cathode ray tube (CRT) displays or thin-film-transistor (TFT) flat panel displays, may be used. These displays are driven by graphics peripherals such as video cards, which in turn are controlled by processors inside the computers.
Traditionally, due to their high cost, flat panel displays have been used only in notebook computers where size and low power requirements are important. As a notebook computer can drive its built-in flat panel display as well as an external CRT display, the video circuit of the notebook computer automatically handles differences between the CRT display and the flat panel display. In the controlled environment of the notebook computer, the maximum resolution of a flat panel display controller may be greater than or equal to that of the notebook computer""s built-in flat panel display. However, in a desktop computer where a particular display attached to the desktop computer may be changed by a user, potential incompatibilities exist when a high resolution flat panel display is used with a desktop computer which is capable of driving only a low resolution flat panel display. For example, certain flat panel capable desktop computers are currently equipped with 65 megahertz (MHZ) video outputs and are limited to a resolution of 1024xc3x97768 pixels. When higher resolution flat panel displays become available, these flat panel displays may be incompatible with the original display circuits.
Computer systems capable of supporting both CRT displays as well as flat panel displays need to handle differences between the two types of display. For example, in the CRT display, an electron beam is swept horizontally across a line of the screen and, at the end of the line, the electron beam is moved vertically down to the next line before the horizontal sweep motion is repeated. Upon reaching the end of the screen, the electron beam is moved back to the origin of the screen and the process is repeated. These timing requirements are referred to as horizontal and vertical retrace timing requirements. The flat panel displays do not require as much time for horizontal and vertical blanking since they are digital devices which are addressed via internal counters and latches instead of an electron beam sweeping motion.
Also, each CRT display inherently has a variable resolution and accepts multiple input resolutions. xe2x80x9cMulti-syncxe2x80x9dcircuitry is used to respond to video signals to control the CRT raster scan frequency. The CRT display""s control signals include vertical sync (VSYNC), horizontal sync (HSYNC), and RED, GREEN, BLUE (RGB) signals. The HSYNC and VSYNC are signals defining horizontal and vertical raster frequency which are synchronized with the CRT display""s logic. RED, GREEN and BLUE are analog signals which contain color data for each pixel. In contrast, the flat panel display operates at a fixed resolution and is controlled by video signals HSYNC, VSYNC, PIXCLOCK, RGBPIXDATA, and DATA_ENABLE. HSYNC and VSYNC are digital signals which provide similar function as the same named signals on a CRT interface. RGBPIXDATA is the digital RGB data and is typically 18-24 bits for each pixel. DATA_ENABLE identifies valid pixel data, which are latched with a pixel clock signal, PIXCLOCK.
Also, a flat panel display controller typically has a maximum resolution limited by a maximum clock frequency supported from its video output circuitry. The controller supports resolutions below the fixed resolution of its flat panel display via circuitry in the flat panel display controller. This circuitry provides at a minimum the ability to center a low resolution display on the panel. Other flat panel display controllers provide circuitry for upscaling the low resolution to the high native resolution of the panel using either pixel replication, or line replication, or interpolation with filtering at various quality levels. However, incompatibilities may exist between the display controller in the computer and the controller in the flat panel display and which may affect the display quality.
An apparatus and a method are disclosed for selecting either a first scaler in a host computer or a second scaler in a display device where the first scaler has a predetermined output quality. The apparatus causes the display device to render a pattern; determines an output quality of the second scaler; and compares the output quality of the second scaler with the predetermined output quality and selecting the scaler with the higher quality output.
Implementations of the invention include one or more of the following. When the display device has a native resolution and the system has an active mode resolution, the apparatus may determine a scaling mode acceptable to the user when the active mode resolution is not equal to the native resolution. Further, data associated with the pattern rendered by the display device may be analyzed. Moreover, the selecting step may include enabling the first scaler if the first scaler provides higher quality output. The selecting step may include enabling the second scaler if the second scaler provides higher quality output. Additionally, the selecting step may include enabling both the first and second scalers if a combination of the first and second scalers provides the best quality. The comparing step may include receiving a user preference; and applying the user preference as a factor in selecting the scaler. A preference for sharpness or smoothness may be specified. Further, the output quality determining step may include collecting horizontal samples from the second scaler; and collecting vertical samples from the second scaler.
In a second embodiment, the apparatus selects either a first scaler in a host computer or a second scaler in a display device, the first scaler being associated with a predetermined display quality. The apparatus has a horizontal line sample buffer for capturing a horizontal line of image data being displayed on the display device; a vertical line sample buffer for capturing a vertical line of image data being displayed on the display device; and means connected to the horizontal and vertical line sample buffers for retrieving data associated with the pattern rendered by the second scaler and for selecting the scaler with higher display quality.
Implementations of the invention include one or more of the following. The apparatus may include a means for determining the output quality associated with the second scaler based on the retrieved data and the output quality associated with the first scaler. Also, the apparatus may include a means for retrieving and analyzing data associated with the pattern may be rendered by the display device. It may further include selecting means which enables the first scaler if the first scaler provides higher quality, or enables the second scaler if the second scaler provides higher quality. The apparatus may also enable both the first and second scalers if a combination of the first and second scalers provide the best quality. Moreover, the comparing means includes a means for receiving a user preference and for applying the user preference as a factor in selecting the scaler. A preference of sharpness or smoothness may be specified. Finally, the output quality determining means may include collecting horizontal or vertical samples from the second scaler.
In another embodiment of the invention, a display mode may be selected in a system where the display controller is capable of supporting scaling or centering. The display mode is associated with an active resolution, a system output resolution, and a centering option. The system determines whether the display device supports scaling; determines a potential scaler mode combination between a display controller scaler and a display device scaler; and allows the user to select one scaler mode combination using a control panel.
Implementations of the invention may include one or more of the following. A control panel option may be enabled if the system action mode resolution is supported by the display device or the display controller. An error message may be generated if the resolution of the display device is not supported by the display controller. The error message may be an audible message. The lowest resolution supported by either the display device or the display controller may be selected if a resolution configuration has not been set. User preferences may be stored and applied automatically when an application selects a new active mode. The acceptable display resolution options may be displayed to the user for the user to select the scaler in the controller and/or in the display device. The user may also select a center mode if appropriate.
Advantages of the invention may include one or more of the following. The video scaling circuit in the flat panel display device avoids a potential resolution incompatibility between the controller in the computer system and the controller in the peripheral flat panel display device. The system also automatically engages the scaler circuitry with the correct scaling factor based on an automatic mode detection process to migrate from a native flat panel display resolution. Further, the system provides software with a user interface for selecting the highest quality of all potential scaler modes when video scalers in the controller and in the display device have overlapping capabilities.
The scaler system is cost-effective since it flexibly handles the cost and quality tradeoffs required on both the system-side and the monitor-side. Cost sensitive systems or displays can implement minimal centering/scaling functions. High end systems can provide high quality scalers and achieve high quality images even when combined with low cost displays. Thus, the system allows the computer to control its ultimate video quality.
Additionally, the invention provides an automatic scaler mode selection process which avoids user intervention and which supports optimum image quality without requiring any expertise in manually configuring the computer and the display device.
The invention also provides a display with an optimized mode centering capability. The invention also minimizes the bandwidth needed between the system and display for centering a lower resolution display mode on a higher resolution display by varying the line frequency so that it is much higher during times where no pixel data is supplied.
Other features and advantages will become apparent from the following description and from the claims.